1. Field of the Invention
The present invention relates to a valve body device, and particularly to an anti-shake flow-limiting cutoff valve.
2. Background of the Invention
When a sudden damage occurs to a faucet or other devices in a pipeline for supplying water or liquid, a lot of water may flow out continuously, i.e., the phenomenon of excess flow appears, which results in waste of water resource. In the prior art, a liquid main switch in the liquid pipeline is manually closed as a remedial measure against the sudden excess flow in the pipeline for supplying water or liquid. However, there is a reaction time between discovering the pipeline damage and closing the main switch, especially when no one is in the field at the time of the accident. In this case, the water resource is greatly wasted. Besides, since the spilling water will flood the floor and furniture in the house, this may bring about loss in property for the user. In a serious case, the spilling water may spread to the surrounding residents, thus leading to more serious consequences.
To this end, a flow stop valve has been proposed to prevent this from happening. The flow stop valve only permits a liquid flow lower than a threshold flux to pass, and does not permit an excess flow to pass. When the flux of liquid is too large, the flow stop valve will be automatically closed, even in an unattended case.
For example, U.S. Pat. No. 5,613,518A discloses a device for restricting excess flow against excess flow in a natural gas pipeline. The device for restricting excess flow is provided with a hollow chamber, which comprises an inlet end and an outlet end. A piston is arranged in the hollow chamber of the inlet end, and an annular shoulder is formed at an end of the hollow chamber which is close to the outlet. A spring is arranged between the piston and the annular shoulder, which applies a set threshold biasing force to said piston that tends to open the inlet end. An annular valve seat is further arranged at said outlet end, which is adapted to block the outlet end of said piston. A radial gap between the piston and the hollow chamber is an excess flow passing channel. Under the cooperation between the spring with a set threshold biasing force and the valve seat in the device for restricting excess flow, the fluid flow can be automatically cut off and the piston can be automatically reset. In a normal situation, under a force from the spring, the piston forms a gap with the valve seat of the inlet end. The fluid flows into the hollow chamber via the gap of inlet end. When a leakage event occurs upstream the device for restricting excess flow, i.e., when an excess flow occurs, the pressure produced by the excess flow exceeds the pressure produced by a fluid of a normal flux. Therefore, the piston will be pushed to move downstream, since the resistance of the spring is overcome. In this way, the piston moves until it rests against the annular valve seat, so that the flow path is closed. The fluid stops flowing to prevent the fluid from continuing to leak.
However, the prior art discussed above suffers from some problems. Firstly, in case of flow overload, said piston shakes at said annular valve seat, so that it is impossible to realize a timely and complete close between said piston and said annular valve seat. The reasons lie in the following aspects. When the piston is subject to an excess flow and thus closes the gap between said piston and said annular valve seat, the fluid flow downstream the piston is suddenly interrupted. At this time, the fluid remaining in the pipeline downstream the piston will flow in the reverse direction, i.e., in the direction from downstream to upstream. Under the resultant force of the impact force produced by the fluid which flows in the reverse direction and the inherent biasing force of the spring, the piston is further made to overcome the pressure produced by the excess flow, and doesn't rest closely against the annular valve seat, thus forming a gap. The above resultant force competes repeatedly with the pressure produced by the excess flow. As a result, the piston repeatedly rests closely against the annular valve seat and then forms a gap between the latter. The repeated processes appear as the above shaking phenomenon. Secondly, even after the shaking process is complete, the following problem still exists. Once the piston rests closely against the annular valve seat, the resting surface of the piston tends to be adsorbed to the annular valve seat. When the problem of excess flow is settled, the spring force of the spring will not always be able to separate the piston from the annular valve seat, thus affecting the normal flow of the gas/liquid flow.